The hydrodynamics of primordial black hole formation  Dependence on the equation of state
Abstract
The dependence of the process for the formation of primordial black holes and their subsequent accretion of gas on the equation of state relating pressure to energy density is analyzed. The Einstein equations for a line element in the spherically symmetric case together with the equation of state are solved numerically for initial conditions consistent with a perturbation within a Freidmann universe. It is found that for equations of state corresponding to an ultrarelativistic gas or somewhat softer, the epoch of primordial black hole formation precedes the epoch of the formation of a physical singularity at the center of the disturbance, which precedes the epoch at which a discontinuity arises in the flow of matter. For the case of a harder equation of state, in which the pressure is on the order of the energy density, the flow discontinuity epoch is found to precede the formation of the physical singularity. It is shown that the softer the equation of state, the more intense will be gas accretion, although catastrophic accretion is impossible. It is concluded that the harder the equation of state of matter, the more difficult it is for primordial black holes to form.
 Publication:

Astronomicheskii Zhurnal
 Pub Date:
 April 1980
 Bibcode:
 1980AZh....57..250N
 Keywords:

 Black Holes (Astronomy);
 Cosmology;
 Equations Of State;
 Hydrodynamic Equations;
 Astronomical Models;
 Flux Density;
 Interstellar Gas;
 Astrophysics